Aircrafts must be able to fly safely with no malfunction or unexpected behavior caused during a cruising flight or during landing and takeoff under high intensity radiated fields (HIRF) as an electro-magnetic environment from radios, televisions, radars, transmitters, and other sources. Therefore, HIRF protection measures required in (14CFR) §§23.1308, 25.1317, 27.1317, and 29.1317, High-intensity Radiated Fields (HIRF) protection, which stipulate Regulations (airworthiness requirements) of FAA (Federal Aviation Administration) need to be taken.
FIG. 7 is a view for explaining an HIRF environment when an aircraft approaches an air control radar antenna of an airport during landing or takeoff. In this case, intensive radiated fields are determined based on a slant range to the antenna and a look angle from the antenna.
Recently, the importance of protection of electric/electronic systems of aircrafts has been significantly increasing because of the following reasons:
1) a greater dependence on electric/electronic systems that execute required functions for continued safe flight and landing of aircrafts;
2) a decrease in electro-magnetic shielding by a certain type of composite material used in design of aircrafts;
3) an increase in susceptibility (sensitivity) of electric/electronic systems to HIRF along with increases in operating speed of data buses or processors, density of ICs or cards, and sensitivity of electronics;
4) an expansion of a usage frequency particularly to a high-frequency band of 1 GHz or more;
5) an increase in severity of an HIRF environment along with an increase in the number of RF transmitters and electric power; and
6) an adverse effect on part of aircrafts when exposed to HIRF.
Meanwhile, inside aircrafts, there may be an adverse effect on, for example, communications with an airport control tower, and communications or control of navigation for a flight along a predetermined route due to radio waves or electro-magnetic noise (simply referred to as electro-magnetic noise below) from various electronics such as mobiles, game machines, and notebook computers, or PEDs (Personal Electro Devices) such as active-type RFID (Radio Frequency IDentification) tags attached to air cargos. Thus, as is well known, passengers are asked to refrain from using various electronics inside aircrafts.
Airframes of aircrafts are generally formed of a metal material, and electro-magnetic noise is thus attenuated. Thus, the electro-magnetic noise enters and exits mainly through windows of a cabin and a cockpit. To prevent the electro-magnetic noise that possibly causes a failure from entering the cockpit or an avionics bay from windows, a film of ITO (Indium Tin Oxide), gold, silver or the like is provided so as to be inserted into a window obtained by laminating a plurality of window panels made of acrylic or the like (e.g., see Patent Literature 1).
Meanwhile, as shown in FIG. 8, various opening portions are formed in an airframe of an aircraft in order to allow boarding, inspection, or the like. Doors for closing the opening portions are generally formed of a metal material of the same type as the airframe.
A gasket seal made of an insulating rubber material is provided on one of the door and the opening portion on the airframe side so as to maintain airtightness and prevent intrusion of water (e.g., see Patent Literatures 2 to 5). Anticorrosion treatment is applied to the other side which the gasket seal contacts by anodizing and coating.